Engineering Water as a Foaming Agent for Polyolefin Foams: A Green and Continuous Strategy

Polymer foams have attracted increasing attention due to their distinctive porous structure and promising application prospects, whereas there remains a challenge in continuously fabricating polyolefin foams by a facile, low-cost, and green strategy. “Puffed corn sticks” are a typical example of Chinese traditional food with a porous structure, which is visually attractive and incredibly delicious. In this study, borrowing the idea from continuously fabricating puffed corn sticks, HDPE has been successfully water-foamed into well-defined internal porous extrudates with different cross-sectional shapes through an extrusion molding method. Herein, water acts as a green foaming agent and the extrusion molding method provides suitable foaming conditions. Under such conditions, polyolefin foams are continuously fabricated by this green strategy. Of note, the current widely used polyolefins can be water-foamed by this strategy, and they can be further extruded into different cross-sectional shapes; therefore, such a water-foaming strategy is of excellent universality. This study proposes a new methodological guidance for the continuous fabrication of polyolefin foams by a green strategy, which will widen the application of polyolefins.